# Question #efdd1

Make sure that you understand that cosine is defined for all real numbers, but secant is only defined where cosine is NOT equal to 0. Therefore, the product $\cos \left(x\right) \sec \left(x\right)$ = 1 everywhere that secant is defined.
cos(x) = 0 when x = odd multiples of $\frac{\pi}{2}$